Method for separating materials



Oct. 13, 1925- 'r. M. CHANCE METHOD FOR SEPARATING MATERIALS med Aug.51, 1923 Jfzzientor:

Patented Oct. 13, 1925.

UNITED STATES PATENTIOFFIVCE'.

FOR SEPARATING MATERIALS.

Application-filed August 81, 1928. Serial No. 660,428.

To all whom it mdyfc'oncem;

Be it known that I, THOMAS M. CHANGE, a citizen of the United States,residing at Philadelphia, in the county of Philadelphia.

8' and State of Pennsylvania, have invented a certain new andusefulMethod for Separating Materials, whereof the following is aspecification.

My invention consists of an improved 10 process for separating materialssuch as ores, coal or the like, from impurities which they contain. 1

The first step my process consists in subjecting the ore or coal to theflotational action ofa fluid mass consistingof a mixture of comminutedsolid matter in liquid, substantially as described in United StatesPatent No. 1,224,138 issued to me on May 1, 1917, in which the lightermaterials will float and the heavier materials will sink, but incarrying out my present improvement the specific gravity of the fluidmass is made.

greater than that necessary to float the lightest of said materialswhich are to be separated by flotation, so that the lightest materialsand also those somewhat heavier than the lightest materials will float,while materials having specific gravities materially greater than thatof the fluid mass will sink; the second .step in the process consists inremoving the lightest of the materials which are floated by said fluidmass, said light materials floating above those of somewhat greaterspecific gravity and in 5 thus causing the said materials of greaterspecific gravity to accumulate in a zone below the zone occupied by thelightest of the floated materials; the thlrd step in the processconsists in the removal of these materials of intermediate specificgravity said removal being efi'ected elther by directly re- 7 movingthese materials from the fluid mass, or by. causing these materials,especially the heavier of these materials, to be carried down with theheavier materials sinking in said fluid mass; and the'fourth step whichmay or may not be essential to the successful use of the process,consists in removing such material of intermediate specific gravity fromthe heavier. materials by which they have been carried down into thelower portion of the said fluid mass.

I will describe the process as applied to the preparation of anthracitecoal, as such description will enable-those familiar with ore dressingor with coal washing to apply the process to the preparation of coal ofany kind or to the washing or concentration of ores.

- Anthracite coal as mined consists of'pieces of relatively pure coal,of pieces of coal of relatively high gravity (that is of high ash), ofpieces of coal having slate or rock interlaminated therewith, of piecesof coal with attached pieces of slate or rock, of pieces of slate withattached coal, and slate, rock or other impurities free from coal. Hencethe specific gravities of the particles of material vary from that ofpure coal, (which for purposes of illustration we may assume to have aspecific gravity of 1.45,) by imperceptible gradations up 'to that of,slate or rock having a specific gravity of 2,50 to 2.60. In using thisprocess in the preparation of anthracite coal I prefer to use a fluidmass with a specific gravity of about 1.65 to 1.70, more or less,although the specific gravity of the pure coal may not exceed 1.45, anda fluid mass of 1.50 specific gravity would be suflicient to float andseparate all of the pure coal from other heavier. materials. By using aspecific gravity greater than that necessary to float the ure coal thefluid mass will also float all 0 the bony or high ash coal, and coalwith slate or rock interlaminated therewith, or coal with small attachedpieces of slate or rock, having specific gravities which approximate toor are less than the specific gravity of the fluid mass, name] 1.65-to1.70, more or less. If a small uantlty of coal tobe separated is fedinto t e fluid mass, so that the quantity of material that will float issuflicient to form a layer, floating at the top of the fluid mass butone particle deep, then all of this floating material including the purecoal, bony coal, laminated coal, etc., will float at the top of thefluid mass and no separation between pure coal and impure coal will beeffected, but if material be fed into the fluid mass at a rate morerapid than the rate at which it is being removed from the fluid mass,then a floating mass of considerable depth will accumulate in a zonenear the top of the fluid mass, and if'the fluid mass be sufiicientlyfluidic, this floatin mass will become, so to speak, stratified inayers, with the purest and lightest coal floating at the top, thathaving a somewhat greater specific gravity floating in contact withbut'below the pure coal and that having a specific gravity approximatingor very little less.

than the specific gravity of the fluid mass floating in the lowerportion of this zone of floating material, it being understood-thatslate, rock, heavy bony coal and heavy laminated coal having a specificgravity greater than that of the fluid mass, have sunk to the lower partof the fluid mass.

The drawing is a vertical cross-section and elevation illustrating oneway in which the method may be carried out, 1 being a tank or receptaclecontaining a fluid mass 2 ofthe described type and superposed upon aclassifier pipe or conduit 3, which is in communication with a refuse(or concentrates) chamber 4 supplied with valves 5 and 6 which may bealternately opened and closed to trap out the materials fallingthroughthe fluid mass 2. An inlet' for liquid (water) under pressure isshown by 7 and the agitation of the fluid mass is accomplished by waterrising through it from 7 and by stir ring arms which are attached totherevolving agitator shaft 8; 9 is a feed chute for feeding intothe'apparatus the materials to be separated, 10 is a partition extendingacross the separating receptacle to confine the lightest of the floatingmaterials to that.

portion of the receptacle to the right of said partition, 11 is an openweir through which the lightest 13, of the floating materials isdischarged and 12 is an-open weir for the discharge of floatingmaterials 14 that are heavier than said lightest floating materials; Thedrawing illustrates how floating coal accumulating in that .part of thereceptacle in the right side of said partition 10 will discharge throughweir 11, and how the less buoyant floating material accumulating belowthe more buoyant material may pass under partition 10, float upwardlythrough said fluid mass and be discharged through weir 12. In thisdrawing the pieces ofmaterials shown all represent coal of differentgrades as to weight, that, 13, floating hi h in the accumulationillustrated to the rig t of partition 10- being of lower specificgravity than that, 14, floating lower in said accumulation. 7

By operating the method in this manner it becomes possible continuouslyto remove the purest coal from'the upper or overlying stratum of thefloating material, and if this method of operation be pursued, theheavier of the floating materials will accumulate in the fluid mass andin some cases those particles having the least buoyancy may bemechanically carried down into the refuse by the slate and rock fallingor sinking through the fluid mass.

The resence below the lightest coal float ing at the top pf the fluidmass, of a floating zone of materialsof somewhat greaterspecific gravityprovides a screen .or barrler to aeaaere prevent pieces of slate androck or other refuse from carrying down pieces of pure coal into therefuse, because the buoyancy of this floating material reduces thefalling velocity of piecesof slate, rock or other heavy material'andreduces the danger of losing good coal With the refuse. This is perhapsespeciall true when material is be ing fed rapidly into the fluid mass,taxing its capacity to effect complete and satisfactory separation.

It is of course evident, when operating the process in this manner, thatif a large quantity of middlings product is thus carried down with therefuse, the refuse can be retreated to recover this product. Suchr'etreatmentcan be carried out by any of the processes in common use forseparating coal, bony coal, laminated coal, etc, from slate, rock andother refuse, with or without recrushing of all or a part of suchproduct.

While the maintenance of a layer of floating material below the zone ofpure coal floating at the top' of the fluid mass is thus useful it willbe understood, of course, that this material can be removed from time totime merely by stopping the feed of material to be separated, for afterthe top layer of pure coal is removed, this heavier material takes itsplace at the surface of the fluid mass, can be similarly removed fromthe fluid mass and either merged with the purer coal or diverted forrecrushing or further treatment. v

My improved process therefore consists essentially in the use of a fluidmass having a specific gravity materially greater than that necessary tofloat or to separate the pure coal from other materials, and in causingthe floated material-s to become tratified separation of the coal andimpure coal with a fluid mass of predetermined specific gravity andwithout, employing two or more fluid masses of different specificgravities or superposed fluid masses of different specific gravitles. I

This description of the process as applied to the separation ofanthracite coal will be sufficient for any versed in the art to applythe process in the concentration of ores, the separation of gangue, etc.

It will, of course, he understood that in retreatin tained, either allor a portion of the said product may be retreated by crushing afidintermediate products thus obseparating the crushed products orotherwise by any of the methods in common use in the washing orpreparation of coal.

My invention is based upon the discovery as above disclosed, thatmaterials of different specific gravities floating in a fluid mass ofthe described type will become arranged approximately in the order oftheir specific gravities, with those of lowest specific gravities at thetop and those of highest specific gravities at the bottom of the zone offloating materials. Slate, rock and other heavy impurities fallingthrough such zone of floating materials will therefore most readilymechanically carry down the lowest and least buoyant of said floatingmaterials. This latter material, being that of highestspecific gravity,is usually a high ash product, comprising laminated coal and slate, coalwith attached slate and heavy bony coal. which it is desirable toseparate from the lighter floating materials which are of lower ashcontent. By thus carrying down this materialavith the refuse, theaverage grade of the floating materials is improved. This relativelyheavy material can be sepa rated from the refuse by any 'method incommon use for the separation of such materials and can be re-crushed tofree the better coal from its impurities and the crushed I productretreated by the herein described or any other method adapted to theseparation .of coal from its impurities.

My invention therefore includes the production and maintenance of a,zoneof floating impure coal in .said fluid mass below, but. in contact withcoal floating at the top of the fluid mass, this zone comprising coal ofgreater specific gravities than that of the coal floating above it, thusproviding a screen or baffle to prevent pure coal from being carrieddown by the falling refuse and at the same time effecting a differentialseparation ofpure coal from impure coal.

I have herein also disclosed the flotation of all tloatable material asa thin layer at the top of a fluid mass of the described type, but I donot herein claim that'method tor-separating materials as it has beenmade the subject of another application, filed simultaneous herewith,for method for separating material. Serial No. 660,429 filed August 31,1923.

llaving described my invention. 1 claim.

1. A method for separating materials of different specific. gravitieswhich consists in immersing said materials in a maintained suspension inliquid of comminuted solid matter of greater specific gravity than saidliquid and substant ally insoluble therein,

and constituting a fluid mass havinga specific gravity materiallygreater than that of the lightest of said materials, the quantity ofsaid materials so immersed being sufficientto form a zone of floatingmaterials of such thickness as to permit said floating materials tostratify in the order of their relative specific gravities; inmaintaining the lower portion of said zone of floating materials as abattle to prevent the heavier falling materials from carrying down thelightest of said materials floating at the top of said fluid mass; incausing materials of greater specific gravity than said fluid mass tosink to the lower part of said fluid mass; in removing thelightermaterials floating in the upper portion of said zone of floatingmaterials and in separately removing the materials comprising the lowerparts of said zone of floating materials, whereby differentialseparation of the said floating materials is effected into grades ofdifferent specific gravities, and in separately removing said heaviermaterials from the lower part ot' said fluid mass.

2. A method for washing coal which consists in immersing said coal withits associated impurities in a maintained-suspension in water of acomminuted solid matter of greater specific gravity than water andsubstantially insoluble therein and constituting a fluid mass having aspecific gravity materially greater than that of the purer particles ofsaid coal, the quantity of said coal so immersed being sutlicient toform a zone of floating coal of such thickness as to permit saidfloating coal to stratify in the order of the relative specificgravities of the particles of said coal; in maintaining the lowerportion of said zone of floating coal as a baffle to prevent heavier andlarger falling particles of said impurities from carrying down pieces ofthe lightest and purest of said coal floating at the top of said fluidmass; in causing impurities of greater specific gravity than said fluidmass to sink to the lower part of said fluid mass; in removing thelightest and purest coal floating in the upper part of said zone offloating coal and in separately removing coal composing the lower partsof said zone of floating coal. whereby differential separation of saidfloating coal is effected into grades of different specific gravities.and in separately removing said impurities from the lower part of saidfluid mass.

lVitness my hand and seal at Philadelphia. Pennsylvania, this 30th dayof August THOMAS M. CHANCE. [1,. st]

